Test constructor calling a method with Sinon

I'd like to ensure that the constructor is calling a method when instantiated with Sinon, however, I can't seem to get this to work, as I believe the sinon is not watching the correct instantiation:

class Test {
  constructor() {
    this.someFunction();
  }

  someFunction() {
    return 1;
  }
}

... and the test

describe('constructor', () => {

  it('should call someFunction()', () => {
    const spyFunc = new Spy(new Test(), 'someFunction');
    expect(spyFunc.calledOnce).to.be.true;
  });

});